Choosing the Right Power Supply



First things first. If you've got a poor-quality and/or faulty power supply, nothing else you do will work to solve your problems. Stick to the basics before you go further...The short answer is to buy a hi-powered, brand name supply, like the new ENERMAX line (430 W or higher) or ANTEC True550. Almost nothing else will do with today's computers. In over 30 years of electronic/computer service, I have found that 85% or more of problems were power-related.

If you want to know more, read on...

Choosing The Right Power Supply

If you?re reading this, there?s a good chance that one of my colleagues or I believe that you could be experiencing problems with your power supply, based upon the symptoms you mentioned in your post, and provided you with this link. Relax, you?re not alone. In 30 years of electronic and computer troubleshooting, I?d say that the majority of the electronic, mainframe, mini, and microcomputer problems I?ve diagnosed and repaired were with the basic power the problematic device was receiving. The symptoms often included random reboots, crashing, the BSOD, lockups, etc.

(As the national support technician for few major computer service companies, working US Defense contracts, I was often the person that had to fly in and correct the problem, or ?walk through? the on-site technician as he closely followed my instructions. I achieved success in my career by carefully reading the manuals, knowing where to go for more information that was otherwise unavailable to me, and/or systematically troubleshooting until the problems were discovered and repaired. I never had the option of giving up.)

The most overlooked component when building or upgrading a PC is the power supply unit (PSU). Some people use their old case and PSU when they upgrade. Some use the PSU that came with their new case. Some people even buy a new PSU. And most inexperienced builders all make the same mistake: The PSU that they?re trying to use is simply inadequate for the job.

Suppose you?re upgrading to a new motherboard, CPU, ram, and video card, but still using the old case and PSU. It?s most likely that you?re upgrading in order to build a machine that is more powerful, faster, has a more colorful display, can number-crunch more quickly, play the latest games, etc. These gains in performance all have one thing in common: They require more raw power. However, have you thought about where that power comes from?

Suppose you?re building a new system with a new case and PSU. Has it occurred to you that the company that you bought the case/PSU from might make more money if they skimp on the supply, even if the supply has a large wattage rating? Most bulk power supply manufacturers don?t make good PSU?s. They use older, cheaper technology, and slap on labels that represent the PSU?s peak outputs, and not their continuous output rating. These companies are intentionally misleading you in order to sell you an inferior product. Brands I avoid when building/repairing my friends? and family?s computers: Allied, Q-Tec, Chieftech, and many others.

For those of you who bought a power supply separately, did you know that you?re only supposed to run a power supply continuously at 30-70% (with 50% being optimal) of its continuous rating for maximum efficiency (which means less heat to you)? Most inexperienced builders either buy PSU?s that are matched to their equipment?s continuous power usage, or ones that are even less powerful than they need. Why? Because they?re trying to save money.

I mean, what?s the fun in a power supply? You don?t get any games with it, there?s no more storage, hardly ever any more bells and whistles, etc. A power supply is boring, and it?s supposed to be, because it?s supposed to provide a stable, reliable platform upon which the rest of the equipment can easily access the amount of power it needs, and when it?s needed. In almost EVERY review of powers supplies, the same point is stressed: Better safe than sorry.

But what does safe vs sorry mean? It can mean that you don?t have to waste money on the wrong PSU in the first place, but it can also mean that you don?t have to replace your expensive ram, CPU, video card, etc. NEEDLESSLY, or because your cheap PSU destroyed them. What? A cheap power supply can wreck your computer? YES IT CAN. A cheap power supply can cause thermal damage, not only from the heat it produces, but also the heat it can create in your components as well. RAM is especially sensitive to heat, and there?s RAM in your CPU, your video cards, and, well, your RAM too. A cheap switching power supply, run at its maximum, or peak, continuously can also destroy components by creating RF (Radio Frequency) signals on your power rails, signals which the components on your peripheral devices were not equipped to handle in the first place.

So this begs the question, how does one choose the right power supply? I?ll illustrate this using my own PC as the example. This is my setup that I use for video processing:

Athlon 2500+ Barton @ 2125Mhz
AMD Retail Heatsink/Fan
2 - 512MB DDR333 w/Thermaltake Spreaders (slot 1&3)
MSI TV@nywhere Video Capture
ATI Radeon 9600
120GB Maxtor DiamondMax Plus 9 SATA
30GB Quantum IDE
Artec CD-R/W

Using this Power Supply Calculator link:

I plug in all my equipment values, but some of this can be a little tricky. For example, since I often run the CPU like an XP 3000, I choose the 3000 as my processor; it?s the same chip run at the faster rate. I also choose the ATI Radeon video card, and I select the RAM wattage for 2 sticks of DDR. I also choose every card I have, like my video capture card, but I also select the boxes for the separate cards that correspond to the functions that my ILSR provides as well (and that I use), like sound, USB, Firewire, NIC, etc. ?Although I use the onboard SATA controller, I don?t select the SCSI PCI card, because, in truth, I?ve probably made up for it by selecting all the other corresponding devices, including cards that the motherboard replaces. I check the boxes for the fans and drives I use, and I?m done, right?

Not yet.

I just remembered that I plan to upgrade soon, so I go back and change the values to reflect my impending changes. I mean, I want to make sure that I have enough power to begin with so that I don?t have to replace the power supply again, right?

Ok. Done. I look at the bottom and see that it tells me that I need a 468 watt PSU. So a 480 watt supply will do, right? Wrong.

Remember that, for efficiency, long-life, and less heat, you want your actual power consumption to fall between 30-70% of the PSU?s rating, so add 30% (minimum) to the 468, and you get 468 + (468*.30)= 608 Watts! Holy Cow!

However, I?d only need a 608-Watt supply if I was using all the devices at once, and I don?t. But, in truth, with video and audio processing, I often get close when I process, burn, and monitor at the same time. (Hardcore gamers also get close a lot, as they blast the sound and push that video to its limits.) So, let?s take off 10% (maximum) of 608, for a total of 541 Watts.

I need a 550 Watt supply, but not just ANY 550 watt PSU. I need a supply that can give me enough power on the critical 3.3, 5, and 12V rails combined. I also want a supply from a trusted, name-brand manufacturer, so I start hitting the many online reviews. Here are just two from Tom?s Hardware:

Read these in their entirety. I didn?t post them because they?re pretty links.

In the end, I chose Antec, because they?ve got the reputation, the recommendation, and because the Antec True550 has better specs than the rest of the 550 Watt competition. I also bought it from a reputable company I found on, for the lowest price I could find, $95.00 shipped to my door. (In truth, I wanted two mini-redundant supplies, like the hospitals and military use, but they were too expensive.)

The result? Not only are the random reboots, crashing, the BSOD, lockups, etc., gone like magic, but I also now have ?peace of mind? in that whatever might happen to my equipment in the future, I know almost for certain that the PSU is NOT the problem. I also bought an UPS, because the East Coast Blackout proved to me that even the Antec True550 isn?t going to provide me any power for emergency shutdown if it doesn?t get its power from somewhere.

Even if your problem doesn?t lie in the PSU completely, it gives you a GREAT platform for troubleshooting further. If you?re not reasonably certain that the supply is the cause, borrow one, or buy one that you can return once you?ve solved the problem. But, above all else, BUY THE RIGHT SUPPLY before you do anything else! Otherwise, you could be plugging and unplugging components, buying and blowing up expensive memory, and causing even further damage, until you give up or die.

I mean, I assume you built your own system to enjoy ?more bang for your buck,? right? What?s the fun of a random reboot in the middle of Unreal Tournament 2003?

William Hopkins
Former Staff Sergeant, USAF
B.A., B.S., with Honors
The University of California, San Diego

P.S. It should be noted that while Enermax, ThermalTake, Zalman, Fortron, and others make great PSU?s, and I compared and considered them, the Antec still won out overall in my critical evaluation, like it did in so may others? reviews. You?d probably be ok if you went with another reputable manufacturer as listed above, but pick a supply that gives you at least 230 watts on the 3.3 and 5V lines combined, and still meets the 30% criteria as stated above. Remember, if the manufacturers don?t give you maximum combined specs up front, they?re untrustworthy right off the bat. With power supplies, you definitely end up getting what you pay for. Don?t say nobody warned you.

P.P.S. Update! After recent developments, it looks like Enermax is the leader, but only the latest line of PSU's.
Good thread but it dosen't answer all my questions.

I have an Enermax Noisetaker 420w (+12v, 15/14A dual rails; +3.3, 32A; +5, 36A).

29A's on the 12 rail - you might think that is enough!(especially when the so called king of PSU's the Antec True 550w only offers 32A i beleive!)
But - I am having all sorts of problems oc'ing my new 939 rig and it is always the addition of extra drives / fans that cause things to change.

Here's my question - Are dual rails bad for overclocking as they limit the power to the CPU and Mobo. For example - maybe my mobo is drawing 18A's and my CPU only 8A's, which combined is 26A's and well within the PSU's limits but, from this example my MOBO is underpowered as the rail only extends to 15A's! (This might be a bad example as I'm no expert on power - but you get where I'm coming from - yes?)

Point is if I didn't have dual rails I would have enough power for my example - period - but with dual rails I would be underpowered - right?

So - Are dual 12v rails bad for large output systems as they are inflexible.

Another guy had the same problem with Enermax 480 and switched to Tagan 480, which has 28A on the 12v (less than his enermax combined rails) BUT he is now rock solid as there is no splitting of the rails).

Help someone please - also this will make this thread very comprehensive if it including a section on dual rails.

Cheers all.
Good article :biggthumbsup:

Only thing I worry about is that I can't see anything mention about the OCZ Powestream 520. I've ordered one of those, and beginning to wonder...have I bought a bad PSU? Please, say it's a good psu...anybody :undecided:
Impressive specs...
33amps on 12v :biggrin:
Idividually adjustable power rails
Shielded cables for VGA and HD

One of the best around so far. If the connectors are silver or gold coated I will be the best I have seen (of specs).

Congrats !
Thx man, good to hear :smile:
Can't wait to get it in my system! Will report any advantages and disavantages soon.

Stay tuned....
o btw my system specs:

asus a7v600
athlon 2500+ @ ~1800mhz (but i may try to push it to ~2100)
1gb ddr400
160gb maxtor 7200
liteon dvd-rom
radeon 9800 pro 128mb (red board)
hercules digifire 7.1 (sound card)
winxp pro sp2
basically its an old design

40a 5v great,but new motherboards and cpu will never use it

as new cpu and vga cards run mostly of the 12v rail

18a 12v

well in a new 64 bit set up thats marginal

i would look else were

dont buy a psu for what you have now

buy for what you hope to have in 2 years time
so, ok. what if instead of buying a new psu which is going to be expensive and i have no idea where to find something better then the one i asked about (except a much more expensive design) so instead of that i can use a diffrent psu (older) just for the vga card. could it do the trick until i manage to get a decent psu?
Originally posted by robig
so, ok. what if instead of buying a new psu which is going to be expensive and i have no idea where to find something better then the one i asked about (except a much more expensive design) so instead of that i can use a diffrent psu (older) just for the vga card. could it do the trick until i manage to get a decent psu?

No that as far as I know wouldn't work, I'd look for an Enermax EG365AX as It has 26 Amps on the +12v rail. It's here on for $77.00($71.00 + $6.00 FedEx) and that isn't really expensive I would think or You could get the 460w Enermax EG465P-VE for $80.00 with Free Shipping and 33 Amps on the +12v rail, It's what I have(the Whisper version).
Originally posted by Thunder
Good article :biggthumbsup:

Only thing I worry about is that I can't see anything mention about the OCZ Powestream 520. I've ordered one of those, and beginning to wonder...have I bought a bad PSU? Please, say it's a good psu...anybody :undecided:

Yeah I've read those OCZ Powerstream power supplys sound real good, But I've never heard of OZC of course. :biggthumbsup: :biggthumbsup: :lol_anim:
i have another idea. what if i do it in revers? i put the older psu (250w) just for my hd and i put the 12v rail on the 300w (not that much a difference) on the gfx card. it could get me enough juice to get the gfx card working right. i think. well im gonna try it and if it works then im gonna use this configuration till i can get my hands on a good psu.
DFI Ultra Infinity A+ Motherboard
40Gb WD 7200rpm hdd
4-80mm fans Thermaltake
xp-m 2500 cpu @ 2.53Ghz
SP-97 w/92mm Vantec Tornado
MSI MX4000 (nVidia) agp card w/128Mb
Kingston Value ram 256Mb PC3200 Dimm
JPAC 500w psu +3.3vdc=28A;+5vdc=40A;+12vdc=18A

This combo should run on a 300w to a 400w psu(Depends on how good the psu is). :biggthumbsup:

So You might try and remove the sound card run Your PC without It until You get a better psu, Like an Enermax EG465P-VE 460w psu(33A on the +12v rail), On It goes for $80.00 shipped. :biggthumbsup: :biggthumbsup:
so your saying not to try the 2 psu`s combo?

i dont have a prob with its price (80$ is ok) but i do have a problem with not having an international credit card to buy it with! and i didnt see it on any of the local stores around here. it seems that nobody really cares about psu`s in israel coz the best i saw was the thermaltake 560w

and its around 160$ and that is twice as much as im willing to pay for a psu especialy since its not so good as you guys say.

and can someone tell me whats the difference between these thermaltake coz they both have the same 3.3/5/12 and different max W (420W / 480W) so... i dont get it:
ok i was able to find the EG465P-VE on a site somewhere around here but it costs 160$!!!!! they sure wanna make a profit..... so i guess i have no other choice but to go for the thermaltake 460W.... o well...
Originally posted by robig
ok i was able to find the EG465P-VE on a site somewhere around here but it costs 160$!!!!! they sure wanna make a profit..... so i guess i have no other choice but to go for the thermaltake 460W.... o well...

Does $160 include shipping? I found It for $86.99 at Legend Micro and Yes They will do shipping to an International location, But You have to email them with Your details first, Otherwise They would cancel the order. Here's the Link to the EG465P-VE(FC) @ Legend Micro.
zoom you are great! thank you and thank you all for your help. now all i need to do is get an international credit card... hopfully with the money the army owns me, it shouldnt be a problem. so again thank you guys for helping out!
Took William's advice and invested in a quality power supply (Enermax Noisetaker 600W) after months of system instability problems. What a difference - for a start my sound card (Soundblaster Audigy) produced four times the volume and more importantly the quality of the sound was dramatically improved! The PC is much quieter and runs a lot cooler. My advice to others if you self build is make sure the basics are right even if it means spending more on the power supply and case and less on the graphics card - afterall you use most of the power supplies features all of the time but how often do you use all of a graphics card features.
i have a "maxpower" psu ,
+12v= 15A
+3.3=20A max combined 3.3v & 5v = 200W

you think it's ok for my pc?

athlon xp 1700+@2600+
2x256mb ddr333
gf4 ti4800se 128mb
2 hdd
case fan
cold cathode..

thanks :D

ps. anyway, i'm thinking in gettin a thermaltake butterfly 480w psu , with PFC, is it good?
Just read your article clarkkent57, and it's awesome. Very nice piece of article. Thanks for sharing your experience. Much appreciated.